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INTENSIONAL PROPERTIES OF POLYGRAPHS
"... Abstract – We present Albert Burroni’s polygraphs as a computational model, showing how these objects can be seen as functional programs. First, we prove that the model is Turing complete. Then, we use a notion of termination proof introduced by the second author to characterize polygraphs that comp ..."
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Abstract – We present Albert Burroni’s polygraphs as a computational model, showing how these objects can be seen as functional programs. First, we prove that the model is Turing complete. Then, we use a notion of termination proof introduced by the second author to characterize polygraphs that compute in polynomial time and, going further, polynomial time functions. 1
Diagram rewriting and operads
, 2009
"... We introduce an explicit diagrammatic syntax for PROs and PROPs, which are used in the theory of operads. By means of diagram rewriting, we obtain presentations of PROs by generators and relations, and in some cases, we even get convergent rewrite systems. This diagrammatic syntax is useful for prac ..."
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We introduce an explicit diagrammatic syntax for PROs and PROPs, which are used in the theory of operads. By means of diagram rewriting, we obtain presentations of PROs by generators and relations, and in some cases, we even get convergent rewrite systems. This diagrammatic syntax is useful for practical computations, but also for theoretical results. Moreover, rewriting is strongly related to homotopy theory. For instance, it can be used to compute homological invariants of algebraic structures, or to prove coherence results.
Computing Critical Pairs in Polygraphs
 In Workshop on Computer Algebra Methods and Commutativity of Algebraic Diagrams (CAMCAD
, 2009
"... Polygraphs generalize to 2categories the usual notion of equational theory, by describing them as quotients, modulo equations, of freely generated 2categories on a given set of generators. In order to work with morphisms modulo the equations, it is often convenient to orient the equations into a c ..."
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Polygraphs generalize to 2categories the usual notion of equational theory, by describing them as quotients, modulo equations, of freely generated 2categories on a given set of generators. In order to work with morphisms modulo the equations, it is often convenient to orient the equations into a confluent rewriting system. In the case of a terminating system, confluence can be checked by showing that critical pairs are joinable. However, the computation of the critical pairs is more complicated for polygraphs than for term rewriting systems: in particular, two left members of a rule don’t necessarily have a finite number of unifiers. We advocate here that a more general notion of rewriting system should be considered instead, and introduce an operad of compact contexts in a 2category, in which two rules have a finite number of unifiers. A concrete representation of contexts is proposed, as well as an unification algorithm for these.
Polygraphic resolutions and homology of monoids
, 2007
"... We prove that for any monoid M, the homology defined by the second author by means of polygraphic resolutions coincides with the homology classically defined by means of resolutions by free ZMmodules. 1 ..."
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We prove that for any monoid M, the homology defined by the second author by means of polygraphic resolutions coincides with the homology classically defined by means of resolutions by free ZMmodules. 1
TOWARDS HIGHERDIMENSIONAL REWRITING THEORY
"... Abstract. String rewriting systems have proved very useful to study monoids. In good cases, they give finite presentations of the monoids, allowing their manipulation by a computer. Even better, when the presentation is confluent and terminating, they provide one with a notion of canonical represent ..."
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Abstract. String rewriting systems have proved very useful to study monoids. In good cases, they give finite presentations of the monoids, allowing their manipulation by a computer. Even better, when the presentation is confluent and terminating, they provide one with a notion of canonical representative of the elements of the presented monoid. Polygraphs are a higherdimensional generalization of this notion of presentation, from the setting of monoids to the much more general setting of ncategories. One of the main purposes of this article is to give a progressive introduction to the notion of higherdimensional rewriting system provided by polygraphs, and describe its links with standard rewriting theory (in particular string and term rewriting systems). After introducing the general setting, we will be interested in proving local confluence for polygraphs presenting 2categories and introduce a framework in which a 2dimensional rewriting system admits a finite number of critical pairs. Recent developments in category theory have established higherdimensional categories as a fundamental theoretical setting in order to study situations arising in various areas of mathematics, physics and computer science. A nice survey of these can be found in [2],
Representing 2Dimensional Critical Pairs
, 2010
"... Polygraphs generalize to ncategories the usual notion of equational theory, thus allowing one to describe a category by the means of generators and relations. When the relations are oriented, such a presentation can be considered as a rewriting system and one might wonder whether the rewriting syst ..."
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Polygraphs generalize to ncategories the usual notion of equational theory, thus allowing one to describe a category by the means of generators and relations. When the relations are oriented, such a presentation can be considered as a rewriting system and one might wonder whether the rewriting system is confluent and terminating in order to provide a notion of canonical representative of morphisms modulo equations (the normal forms of the morphisms). In term rewriting systems, confluence is often proved by computing the critical pairs, which are in finite number, and showing that they are joinable. We extend here this methodology to polygraphs presenting 2categories. This task is not straightforward because a finite polygraph might admit an infinite number of critical pairs. This leads us to introduce the multicategory of contexts of the free compact 2category generated by a 2category, in which we can embed the original 2category generated by the polygraph and compute a finite number
Team Pareo Formal Islands: Foundations and Applications
"... c t i v it y e p o r t 2008 Table of contents ..."
5 POLYGRAPHS FOR TERMINATION OF LEFTLINEAR TERM REWRITING SYSTEMS
, 2008
"... Abstract – We present a methodology for proving termination of leftlinear term rewriting systems (TRSs) by using Albert Burroni’s polygraphs, a kind of rewriting systems on algebraic circuits. We translate the considered TRS into a polygraph of minimal size whose termination is proven with a polygr ..."
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Abstract – We present a methodology for proving termination of leftlinear term rewriting systems (TRSs) by using Albert Burroni’s polygraphs, a kind of rewriting systems on algebraic circuits. We translate the considered TRS into a polygraph of minimal size whose termination is proven with a polygraphic interpretation, then we get back the property on the TRS. We recall Yves Lafont’s general translation of TRSs into polygraphs and known links between their termination properties. We give several conditions on the original TRS, including being a firstorder functional program, that ensure that we can reduce the size of the polygraphic translation. We also prove sufficient conditions on the polygraphic interpretations of a minimal translation to imply termination of the original TRS. Examples are given to compare this method with usual polynomial interpretations. 1